For many women treated for breast cancer, finishing chemotherapy and surgery is a huge relief.
But even after successful treatment, there is always a concern that the cancer could return months or even years later.
Today, doctors usually look for recurrence using scans such as CT scans, mammograms, or MRI imaging. Patients are also monitored for symptoms such as pain, coughing, weight loss, or unusual lumps.
The difficulty is that breast cancer recurrence is often only discovered once tumors become large enough to see or once symptoms begin. By then, the disease may already have spread to other parts of the body.
Researchers at Lund University now believe a simple blood test could help doctors detect recurrence much earlier.
Their new study, published in EMBO Molecular Medicine, describes a blood-testing method called Pathlight that can identify tiny traces of tumor DNA in the bloodstream long before cancer becomes visible on imaging tests.
The researchers say this technology may eventually help doctors monitor breast cancer patients more closely and tailor treatment more accurately.
Every cancer contains unique genetic changes. These genetic changes act almost like a fingerprint that makes one tumor different from another.
As cancer cells grow and die, they release small fragments of DNA into the blood. Scientists call this circulating tumor DNA.
The new Pathlight method searches for these specific tumor DNA fragments in blood samples.
According to Professor Lao Saal from Lund University, the system is sensitive enough to detect extremely tiny amounts of tumor DNA with very high precision.
This is important because after treatment, only a very small number of cancer cells may remain in the body. Traditional scans may not detect them for months or even years.
The researchers wanted to understand whether the blood test could predict future recurrence and also help measure how well treatment was working.
To investigate this, they followed 136 breast cancer patients who received chemotherapy and surgery.
Blood samples were collected throughout treatment and recovery. Researchers tested samples taken at diagnosis, during chemotherapy, after surgery, and during long-term follow-up care for up to six years.
The results showed strong links between tumor DNA and future cancer relapse.
Among patients who later developed metastatic disease, the blood test detected signs of returning cancer a median of 13.8 months before recurrence became clinically visible.
In several cases, tumor DNA was found nearly four years before standard medical methods detected the disease.
Researchers say this could potentially transform breast cancer follow-up care.
Earlier detection may allow doctors to start treatment sooner, possibly before cancer spreads further or becomes more difficult to control.
The study also provided information about treatment response.
Before treatment started, tumor DNA was detectable in nearly 90% of patients.
After chemotherapy but before surgery, about 21% of patients still had detectable tumor DNA in their blood.
The researchers believe this may indicate that some cancer cells survived treatment.
Another important finding involved patients whose tumor DNA levels failed to decrease clearly during treatment. Around 13% of patients fell into this category, and they had a significantly higher risk of recurrence later.
This suggests the blood test may help identify patients who are not responding well to chemotherapy much earlier than current methods.
At present, doctors commonly rely on something called pathological complete response, or pCR, to evaluate treatment success before surgery. This means doctors cannot find remaining cancer cells in tissue samples after chemotherapy.
However, the new blood test appeared to predict future relapse risk even better than pCR.
Researchers believe this could help doctors personalize breast cancer treatment in the future.
Patients identified as high risk might benefit from stronger follow-up treatment or more intensive monitoring. Patients identified as lower risk may avoid unnecessarily aggressive therapies and some of the side effects that come with them.
The researchers also say the new method has practical advantages.
Some genetic testing technologies are highly detailed but extremely expensive and time-consuming. Pathlight provides less detailed information, but it is faster, cheaper, and still accurate enough for monitoring treatment response and recurrence risk.
This may make it easier to use more widely in healthcare systems.
Still, the scientists stressed that the technology is not ready to replace standard monitoring methods yet.
More studies involving larger patient groups are needed to confirm the results.
Researchers also need to answer important medical questions. For example, doctors still do not know whether treating patients earlier based on blood-test results alone will actually improve survival or long-term health outcomes.
There is also the emotional challenge of telling patients that tumor DNA has been detected before visible cancer appears. Doctors would need clear guidelines on how to use this information safely and effectively.
Even with these unanswered questions, many cancer experts view liquid biopsy technology as one of the most exciting developments in modern cancer care.
Blood-based cancer monitoring is less invasive than traditional biopsies and may allow doctors to track cancer continuously over time.
The Lund University study suggests that future cancer care may become more personalized, earlier, and more precise.
Overall, this research is very important because it shows that tiny traces of cancer may be detectable long before traditional scans reveal disease recurrence. The technology appears highly sensitive and may help doctors identify high-risk patients earlier than current approaches.
However, the study is still relatively small, and more evidence is needed before the test becomes routine in hospitals. Scientists must still prove that earlier detection through tumor DNA monitoring leads to better survival and treatment outcomes.
Even so, the findings represent a major step forward in the growing field of blood-based cancer testing and personalized medicine.
